Rising Star Expedition – National Geographic Society (blogs)http://voices.nationalgeographic.com/blog/rising-star-expedition/
Ideas and Insights From Our CommunityFri, 09 Dec 2016 14:53:38 +0000en-UShourly1https://wordpress.org/?v=4.6.1102104349What Can We Learn From Homo naledi’s Skull?http://voices.nationalgeographic.com/2015/09/17/what-can-we-learn-from-homo-naledis-skull/
http://voices.nationalgeographic.com/2015/09/17/what-can-we-learn-from-homo-naledis-skull/#commentsThu, 17 Sep 2015 21:26:03 +0000http://voices.nationalgeographic.com/?p=166660After the excitement of Homo naledi’s discovery and extraction from deep in a narrow cave in South Africa, and the implication that these non-humans may have intentionally carried their dead deep into the earth, we are left with the bones themselves, what they tell us about these creatures, and what new questions they inspire.

These sketches and notes come from interviews and conversations during both the 2013 Rising Star Expedition and the 2014 workshop where established experts and early-career scientists came together to analyze the 1,550 fossil pieces.

The Skull

Modern humans have a very large, high-arching, round cranium (or brain case), and the mandible (or lower jaw), is positioned directly below the front half of the skull.

A very early hominin like an australopithecine (“southern ape”) such as Lucy, has a much smaller, almond-shaped cranium (not that there’s much of Lucy’s actual cranium to go by—this comes from other specimens), with the mandible jutting out in front of the face.

Homo naledi is in the interesting position of having a very small skull, but a very round one, and there is only a shallow slope down from the nose to the teeth.

This is similar to what is seen in Australopithecus sediba, also found by Lee Berger nearby, which while not in the genus Homo, shares more skull shape traits with us than with other australopiths. (Quick Guide: Know Your Hominid Skulls)

That roundness of the skull and flatness of the face are both related to having smaller teeth and chewing muscles, relative to our other relatives. So they probably ate more like us than say chimps or gorillas do.

N.B. on Nose Bones

The jaw changes have other impacts on our facial appearance as well. Instead of thinking that human noses jut out while other ape noses lie flat, to a certain extent you can actually picture that as our our jaws shrank and scooted back, they left our noses sticking out all alone in the front. (Further adaptations then gave the noses of some human groups much more prominent bridges.)

Tiny Skull

The small size of the skull is one of naledi’s surprises. For a long time, large brains have been considered a defining characteristic of the genus Homo. No one expected to find a creature with so many physical attributes of our genus, but with a brain the size of an orange (smaller than a modern chimp’s!). Neurologists will tell you though that the volume of a brain is less important to its abilities than the structure. It raises interesting questions about what the mental capacity of naledi might have been.

There is always the chance that a tiny skull is just from a juvenile. Here though, the bones themselves make the answer clear. First off, the sutures that close between the different skull elements as we grow are all clearly in an advanced state. The more exciting piece of evidence though is that there’s not just one skull, there are pieces of five—and they’re all about the same size.

All Together, Boys and Girls

That brings up another point though: each skull falls into one of two groups: the slightly larger and the slightly smaller (by about 15 percent), which the team members see as male and female, respectively.

Having only a small difference between the physical size and appearance of the sexes is another one of the intriguing aspects of Homo naledi. It is too early to apply this reliably to a newly discovered species, but studies of chimps and bonobos, as well as wolves and dogs, wild and tame foxes, and even human facial preferences, show that smaller, rounder skulls, and lesser differences between the sexes are connected to a selection for tameness, whether through outside pressures or the individual choices of mates.

Long Before Porches or Rocking Chairs

There is one other aspect of the naledi skulls that might give an early clue to their social or emotional lives: the teeth and bone of one mandible are so worn down that they would have come from an individual of considerable age. Combined with the implication that these individuals were all intentionally put into this cave by other members of their group, such a jawbone hints at a story of keeping a group together for multiple generations, and supporting members with impaired capabilities.

]]>http://voices.nationalgeographic.com/2015/09/17/what-can-we-learn-from-homo-naledis-skull/feed/8166660Homo naledi’s Nike-Ready Foothttp://voices.nationalgeographic.com/2015/09/16/homo-naledis-nike-ready-foot/
http://voices.nationalgeographic.com/2015/09/16/homo-naledis-nike-ready-foot/#commentsWed, 16 Sep 2015 19:48:16 +0000http://voices.nationalgeographic.com/?p=166661After the excitement of Homo naledi’s discovery and extraction from deep in a narrow cave in South Africa, and the implication that these non-humans may have intentionally carried their dead deep into the earth, we are left with the bones themselves, what they tell us about these creatures, and what new questions they inspire.

These sketches and notes come from interviews and conversations during both the 2013 Rising Star Expedition and the 2014 workshop where established experts and early-career scientists came together to analyze the 1,550 fossil pieces.

The Foot

There was a recurring comment at the workshop in June, 2014, that analyzed the first batch of remains of what would come to be called Homo naledi: The body seemed primitive in the core, but more human at the extremities. It was as though the body parts that contacted the physical world most directly were adapting to new conditions and uses, but news of the innovations hadn’t yet reached the heartland.

The foot was a big part of this.

During the excavations in November, 2013, before the foot bones proper were found and reassembled, a single bone from the ankle widened eyes and led the team to expect that whatever this creature was, it was pretty efficiently bipedal.

The bone was the talus, which sits right below the tibia, or shin bone, and it had a remarkably level top. In humans, the top of the talus is level from side to side, allowing the leg to rotate directly over the foot in the path of motion. In other apes, the top of the talus is tilted toward the inside of the foot which meets with the angled bottom of the tibia, causing the leg to rotate over the foot at an angle, giving them a bowlegged appearance. (This is possibly why the guys in Planet of the Apes are such fine horsemen. Err, “horseapes.”)

So before a single toe was found, the team had an idea of what to expect.

When the toes were finally unearthed, they were found to be slightly curved, but mostly straight, with the big toe coming up right alongside the others. For anyone else who’s ever wished they could use their feet like hands, Homo naledi was no better off than we are. What it lacked in gripping ability though, naledi’s foot made up for with support and efficiency of back and forth motion.

The feet of bonobos and other apes have an arch similar to ours that runs from the heel to the toes, but they are mostly flat from the inside to the outside. Naledi however begins to show the “transverse arch” that literally puts a spring in your step. This dual-arching structure wouldn’t do much for an animal that’s shuffling with a side-to-side sway or leaning forward on its hands, but like the arches in a cathedral holding up a soaring ceiling, it does wonders for someone walking with all their weight balanced over those two back feet.

When the first bones emerged from the cave, no one knew what creature they had come from. With feet made for walking like us, dexterous thumbs, and a nice round skull though, it soon became clear that whatever it was, it was remarkably familiar looking.

The stories of its discovery and excavation make Homo naledi unforgettable, but its bones are what make it like us.

]]>http://voices.nationalgeographic.com/2015/09/16/homo-naledis-nike-ready-foot/feed/5166661Homo naledi’s Powerful Hand Up Closehttp://voices.nationalgeographic.com/2015/09/16/homo-naledis-remarkable-hand/
http://voices.nationalgeographic.com/2015/09/16/homo-naledis-remarkable-hand/#commentsWed, 16 Sep 2015 19:46:40 +0000http://voices.nationalgeographic.com/?p=166642After the excitement of Homo naledi’s discovery and extraction from deep in a narrow cave in South Africa, and the implication that these non-humans may have intentionally carried their dead deep into the earth, we are left with the bones themselves, what they tell us about these creatures, and what new questions they inspire.

These sketches and notes come from interviews and conversations during both the 2013 Rising Star Expedition and the 2014 workshop where established experts and early-career scientists came together to analyze the 1,550 fossil pieces.

The Hand

Now maybe everyone just had rock-climbing on the brain since that’s what it took to recover the bones of naledi from the cave.

But that said, during its excavation, as the various finger bones were extracted and laid out, it was clear that Homo naledi could have given Alex Honnold a run (or a climb) for his money.

The first clue to the strength of these hands was the size and shape of the thumb. The bones themselves are longer in proportion to the other fingers than ours are, and the contours of the bones show they had very large muscles attached.

Other apes have long palms and fingers, with smaller thumbs kept out of the way down by the wrist. Their hands are enormously powerful, with an average female chimp having the grip strength of an NFL linebacker, and they can obviously climb with ease and dexterity.

Human thumbs on the other hand (so to speak) are more like equal players with the other fingers. They are similar in size and range of motion, which is great for manipulating objects with precision, but the reduced size of the fingers and palms makes them weaker, and the prominent thumb is prone to painful snags if we try to swing through the trees.

Naledi seems to have the best of both worlds. Like humans and australopithecines such as sediba (Lee Berger’s other big find), the thumb is opposable, but uniquely, it is also huge and muscular. That’s intriguing, but alone it’s not evidence that the creature was a good climber. For that there is another clue.

We might tend to think of a skeleton as basically a steel superstructure our muscles are draped over, but our bones are living, growing, and changing based on use just as much as the rest of us. For climbers of all sorts, the suspension of weight and the repeated strong gripping applies stresses that induce the digits of the fingers to curve. This is visible in x-rays of athletes, and it’s visible in the bones of naledi’s fingers as they rest in your hand.

Since the naledi find has not yet been dated, we do not know if the creatures lived among dense forest or open savanna, and so whether they would have spent much time in and among trees. Regardless of the groundcover though, the ground itself would have been largely the same: undulating hills with rocky outcroppings and caves everywhere.

Climbing could certainly have been an advantage, and naledi would have had to rely on strong hands to do it­. Its feet wouldn’t have been much help. They were too much like ours.

]]>http://voices.nationalgeographic.com/2015/09/16/homo-naledis-remarkable-hand/feed/8166642How the Naledi Team Solved a 1,550-Piece Puzzlehttp://voices.nationalgeographic.com/2015/09/15/how-the-naledi-team-solved-a-1550-piece-puzzle/
http://voices.nationalgeographic.com/2015/09/15/how-the-naledi-team-solved-a-1550-piece-puzzle/#commentsTue, 15 Sep 2015 20:42:48 +0000http://voices.nationalgeographic.com/?p=166594The announcement of Homo naledi last week was just the latest phase of a scientific adventure that’s been going on for two years in and around a tiny cave in South Africa.

It started in November, 2013, with the three-week long expedition to recover what National Geographic Explorer-in-Residence Lee Berger and team at first thought were bones from a single ancient hominin. We lived in tents, swapped theories around a fire, and I wrote about it all daily for this expedition blog. (Relive the discovery by reading the original posts in order.)

The scientists were chosen for their excavation skills and ability to fit through tight spaces. I’d like to think I was chosen for my writing skills, but being roughly Tom Cruise sized, I have a sneaking suspicion they may have had more practical “emergency uses” for me in mind.

Back in the Lab

The above video gives a glimpse of phase two of the project: a six-week workshop six months later, when established experts and early career scientists gathered in Johannesburg to make sense of the 1,550 fossil pieces the team had recovered. This time we were in hotel rooms, not tents, and the closest most of us came to getting into a cave was entering the newly renovated fossil vault at the University of the Witwatersrand.

Glass-fronted cabinets full of fossils and replicas lined the walls. The central area contained Tetris-like configurations of folding tables at which sat groups or pairs of researchers, each focused on a particular section of anatomy or area of analysis.

Several of the “Underground Astronauts” were there the week I visited: Elen Feuerriegel studying the arm and shoulder; Alia Gurtov tucked away in the “tooth booth”; Marina Elliott hosting a geologist down into the fossil chamber to investigate the context of the bones.

It was a diverse group facing the “busiest, messiest 3-D puzzle ever” as Elen called it.

In a matter of a few weeks, the team members contributed thousands of hours of work, comparing the fossils with casts of other hominins, creating and analyzing 3D images of the bones, and running statistical analyses. The heavy vault door stayed cracked open as people scurried in and out for a meal or to pick up the latest model from the ever-whirring 3-D printer.

Berger’s Big Idea

Two years from dirt to desktops is a pretty unusual turnaround for such a major find. The nearly complete skeleton of “Little Foot,” discovered more than 15 years ago just a few miles away from the H. naledi site, has yet to be fully described in the scientific literature.

That kind of delay is what Lee was hoping to avoid. Such a large amount of new material is inherently relevant to practically any study of early hominins, and with so many bones recovered, and so many more still in the cave, he didn’t want the paleoanthropology community (or the public) to have to wait.

He also wanted cross-pollination of ideas for the researchers. “You interact with experts on all parts of the body,” said Damiano Marchi from the Università di Pisa, working on the lower limb, “and it gives an overall understanding of the morphology and function.”

Lee and his collaborators would like to see the famously slow and siloed field of paleoanthropology handled this way in general: Find something, get a large team involved, get the results out quickly, open up access to the fossils—and then go find more bones.

Not So Fast?

Not everyone in the field agrees. Some critics point to possible errors from inexperienced team members, who may lack the perspective of seasoned paleoanthropologists. Others say it simply takes more time to analyze material thoroughly. Since hominin fossil finds have generally been rare, researchers also tend to keep them closely guarded, accessible only by the discoverer and trusted colleagues. Berger thinks the greater risk is not to try new approaches.

He knows the workshop might have the appearance of people working too fast, but that’s in appearance only, he says. “This is a marathon, not a sprint—even though it looks like a sprint.”

And as to what it’s like to work this way, “the reward is more than stress,” Damiano Marchi told me. “It’s a very, very stimulating environment. This experiment worked.”

Watch the Two-Hour Special: The NOVA/National Geographic documentary, “Dawn of Humanity,” premieres in the U.S. Sept. 16, 2015, at 9 p.m. ET/8 p.m. CT on PBS.

]]>http://voices.nationalgeographic.com/2015/09/15/how-the-naledi-team-solved-a-1550-piece-puzzle/feed/4166594Homo naledi: 1,500 Fossils Revolutionize Human Family Treehttp://voices.nationalgeographic.com/2015/09/10/homo-naledi-1500-fossils-cave-revolutionize-human-evolution-family-tree/
http://voices.nationalgeographic.com/2015/09/10/homo-naledi-1500-fossils-cave-revolutionize-human-evolution-family-tree/#commentsThu, 10 Sep 2015 09:06:13 +0000http://voices.nationalgeographic.com/?p=166371A composite skeleton of Homo naledi is surrounded by some of the hundreds of other fossil elements recovered from the Dinaledi Chamber in the Rising Star cave in South Africa in this photo from the October National Geographic magazine. The expedition team was led by National Geographic Explorer-in-Residence Lee Berger of the University of the Witwatersrand. The find was announced by the University of the Witwatersrand, the National Geographic Society and the South African National Research Foundation and published in the journal eLife. (Photo by Robert Clark/National Geographic; Source: Lee Berger, Wits, photographed at Evolutionary Studies Institute)

Two years after being discovered deep in a South African cave, the 1,500 fossils excavated during the Rising Star Expedition have been identified as belonging to a previously unknown early human relative that National Geographic Explorer-in-Residence Lee Berger and team have named Homo
naledi.

With at least 15 individuals of all ages and both sexes represented, the find adds an unprecedented amount of information to our understanding of early human evolution in Africa.

Just as striking, the absence of any other animal remains or large debris in the fossil chamber strongly suggests that these creatures intentionally deposited their dead within the cave. Until now, only modern humans and Neanderthals had been known to practice burial.

The NOVA/National Geographic documentary, “Dawn of Humanity,” chronicles the discovery and premieres in the U.S. Sept. 16, 2015, at 9 p.m. ET/8 p.m. CT on PBS in the U.S. and is streaming online now.

Join the discussion surrounding this remarkable discovery here and on Twitter using #NalediFossils.

Every day at Rising Star is a busy one, but in our free time we’ve been lucky to make some local friends who follow the expedition and this blog. Thanks for helping us feel welcome in South Africa!

Today marked the last day of excavation for this round of Rising Star. In only eight days of digging, we retrieved more than 320 numbered fossil specimens and an awful lot of sediment. Don’t worry: an untold number of fossils, some sure to be spectacular, remain in the chamber waiting to be excavated in the not too distant future.

Why didn’t we get them all? First, it would take a very long time. All of the fossils we collected this time came from a small area of the total chamber floor. Second, archaeologists often like to preserve part of a site in the ground for study later. Future advances in technology and new research questions might alter how we’d excavate so leaving some areas undisturbed actually allows us to learn more from the site and the fossils down the road.

The End of the Day
As Marina Elliot and I were taking the last photos and making the final scans, we were joined by our intrepid cave explorers and support team of Steven Tucker and Rick Hunter.

Proof that ancient hominins had computers? Nope, just a shot of the team lugging elements of this season’s command center out of the cave. (Photo courtesy Becca Peixotto)

Marina and I escorted bags of fossils, sediment, and equipment up through the famous chute with Rick hauling them on a rope from above. It’s tight in the slot with a person and a heavy bag. With a fair bit of grunting and some great cooperation, we got the bags up the chute, down Dragon’s Back, through Post Box, up the Ladder and to the surface.

Meanwhile, Steven was busy securing the cameras and lights from the harsh cave environment since they will sit there dormant for a few months. Everything else—every scrap of paper, bubble wrap and toothpick—was packed up and carried out of the cave. We didn’t say goodbye to the Rising Star cave, rather “thanks for an incredible week and see you again soon!”

Here Peter Schmid is hard at work at his desk in the cave. Swap out the background for an office, and this is pretty much how things will look for the coming weeks as well. (Photo by Ashley Kruger)

Next, we’ll be working in the lab with Peter Schmid sifting through the sediment looking for still more fossils we may have missed. Tiny as they may be, each bone and fossil fragment provides another clue to mystery of the Rising Star fossils.

]]>http://voices.nationalgeographic.com/2014/04/01/wrapping-up-round-two/feed/2128994Young Visitor Helps Recover First Top Jaw From the Sitehttp://voices.nationalgeographic.com/2014/03/29/young-visitor-helps-recover-first-top-jaw-from-the-site/
http://voices.nationalgeographic.com/2014/03/29/young-visitor-helps-recover-first-top-jaw-from-the-site/#respondSat, 29 Mar 2014 07:37:49 +0000http://newswatch.nationalgeographic.com/?p=128478After months of anticipation, the section of hominin top jaw is finally recovered from the cave. (Photo by Lee Berger)

By Becca Peixotto

Today, our fourth day underground, we had a special guest in the command center.

Young Stefan from a school here in South Africa got to be a paleoanthropologist for a day and by watching the video monitors and speaking to us via the phone-style voice comms system guided Marina and me through recovering the 151st numbered specimen from this round of excavation.

We did not get to meet this promising scientist-in-the-making in person but could certainly sense his excitement about doing paleoscience when we talked with him over the intercom from down in the chamber. Thanks, Stefan for your help today!

State of the Excavation
At the end of the day today, the Puzzle Box area looks very different from the November photos.

The time spent planning and discussing on Monday was invaluable but excavations like those here at Rising Star are dynamic events and no plan on a project like this ever set in stone.

We accomplished our initial goal of recovering the maxilla (the part of a skull containing the upper teeth) and long bone that have been calling out to us since their initial uncovering four months ago.

This long bone was one of the earliest pieces to be uncovered, but its size and orientation prevented easy removal throught out the November dig because with each bit revealed, other bones were found on top or adjacent to it.

In the process, of finally accomplishing this goal, we also made new finds that prompt us to change our plans and create new goals for the rest if out time here this week.

The fossil record in this area of the site we call UW-101 is rich and fascinating. I look forward to whatever discoveries tomorrow may bring.

]]>http://voices.nationalgeographic.com/2014/03/29/young-visitor-helps-recover-first-top-jaw-from-the-site/feed/0128478What’s New at This Week’s Excavationhttp://voices.nationalgeographic.com/2014/03/28/whats-new-at-this-weeks-excavation/
http://voices.nationalgeographic.com/2014/03/28/whats-new-at-this-weeks-excavation/#commentsSat, 29 Mar 2014 02:50:56 +0000http://newswatch.nationalgeographic.com/?p=128472The Control Center display shows three views of Marina Elliott and Becca Peixotto at work removing fossils from the area called the Puzzle Box. (Photo by Lee Berger)

By Becca Peixotto

At the beginning of the week, Marina Elliott, Lee Berger, Peter Schmidt, and I sat in Lee’s office at Wits University studying photos from last November of the area of high density of fossils we call the “Puzzle Box.”

We set priorities for this week’s renewed excavation, imagined contingencies, reviewed equipment, and, always important for archaeologists, discussed methodology and procedures.

With any find, but particularly with one of this significance, we don’t just grab what we see willy-nilly. There is a body of theory and practice behind what we do.

Just like last November, we will still 3D scan and photograph every step of the way to ensure thorough documentation, use toothpicks and bamboo tools to limit the damage to the fossils, and bag and bring to the surface all the sediment so it can be searched in the lab for the tiniest fossil fragment and other clues about the site. However, with the benefit of hindsight and Ashley Kruger’s countless hours rendering the 3D scans, we have modified some of the procedures to make digital recreation of the excavation easier and faster. That will aid the analysis and interpretation of both individual bones and the site as a whole.

We didn’t descend into the cave until the next day, but that meeting and our afternoon visit to Rising Star left Marina and I even more excited to get back to work.

Slimmed Down, But Still Strong
John Hawks mentioned in his post earlier this week that this is a slimmed down version of the original Rising Star Expedition. We are only about ten on site at any given time: two caver/scientists, three cavers providing safety and support, one logistics guru, and two to three senior scientists and technology specialists at a mini-command center just inside the entrance to the cave.

Instead of living in a small tent city on-site, we’re commuting to the cave each day, leaving Johannesburg before daybreak (to beat the traffic), and bringing fossils back (usually through heavy traffic) to Peter in the Wits lab every afternoon.

The expedition may be smaller and more muted this time but our collective enthusiasm for the cave, for science, and for the process of discovery is as lively as it was last November: each new fossil generates oohs and aahs, cheers, and giggles of excitement.

Changes Underground
It’s not only the structure of the expedition that’s different this time around. The cave itself has changed too.

Caves like Rising Star are living, breathing geological formations and are affected by natural and human-caused changes both within the cave and above ground.

The late summer in the Cradle of Humankind this year was remarkably rainy. In karst regions like this, rainwater does not stay long on the surface in creeks or rivers. Instead it quickly seeps through cracks in the dolomite.

The potential for water to seep into the caverns through the porous rock overhead is great, and could affect the fossils below. (Photo courtesy Becca Peixotto)

The water sometimes pools in the caves, like the chilly puddle at the narrowest squeeze in the Postbox belly-crawl. No staying dry in that one! The water may hang in the air like it does in the final chamber where there is no standing water but where the humidity registers on our air monitors at 99.9%, or the rainwater may become part of an existing drip, dissolving the dolomite and slowly depositing calcium carbonate as a stalactite or other speleothem.

It is amazing to think the constant drip-drip-drip is creating one of these beautiful features at least for this season faster than normal (it will take many, many years to notice the growth of the formations). Still, it comes as a bit of shock when a cold drip unexpectedly lands on the back of your neck while you’re busy delicately moving sediment away from a fossil.

As the water percolates through the rock, it dissolves minerals and then carries them along as it drips into open areas. The accumulating minerals form stalactites where they hang, and stalagmites where they drip to the floor. (Photo courtesy Becca Peixotto)

This week, a small targeted excavation is underway at Rising Star, involving some of the original core team of excavators — Marina Elliott and Becca Peixotto, and cavers Pedro Boschoff, Rick Hunter and Steven Tucker, along with key personnel Ashley Kruger, Justin Mukanku, Wayne Crichton, Peter Schmid and Lee Berger. Cavers descended yesterday to rig safety ropes and equipment, and to make sure the wiring and camera systems are still operational. Instead of rebuilding the Command Center tent from November, this time we’ve set up the phones, tables, computers, and more inside the cave entrance. This makes our working conditions a bit cooler in every sense of the word. Everything is in place, and today excavation work began.

The initial goal of this work is to recover a hominin maxilla that is exposed in the original “puzzle box” excavation area. As the November expedition was drawing to a close, the excavation team uncovered this maxilla. When they were working that area, the excavators carefully cleared around each fragment of bone before removing it. That’s how they first uncovered the maxilla.

Although they could carefully work around it, they couldn’t bring it out of the sediment because of the overlying bones. It broke everyone’s hearts to leave that piece in situ, but at the time, we estimated it would be at least two additional full days of careful excavation work to bring it out. The team will soon see whether that was right, or whether it was an underestimate!

The University of the Witwatersrand has been busily planning for the May workshop, during which the team will work to describe the fossil collection to date. More than 25 early career scientists have now accepted positions in the workshop, representing 11 different countries. It is an exciting group and I will be very pleased to see them come together to work on the fossils.

The work underground this week is pursuing two major targets in preparation for the workshop. One is obviously that maxilla. Any paleoanthropologist knows the importance of the face to understanding the relationship of fossil hominins. We have most parts of the skeleton represented in the collection, including many maxillary fragments. But since we know that relatively complete maxilla is there in the deposit, the science team believes we need to include it in our analysis. That maxilla won’t come out by itself, though — it’s sitting under other bones that will have to be excavated first.

The maxilla and a long bone protrude from the ground, as they were left at the end of the November expedition.

The other target this week is the 102 site. We recovered a substantial amount of skeletal material from 102 in February. But we don’t yet know enough about this assemblage to understand how it compares to site 101. Understanding that relation is very important for us as we try to work out the circumstances in which the hominin sample accumulated in the cave. Obviously, if these are two independent occurrences representing different kinds of hominins, we want to know that!

This week will tell us something else very important about the site. In November, we worked at high intensity for three weeks underground, with a team of six excavators and all the attendant support staff. This week is a much smaller-scale enterprise, with fewer people working longer shifts. The team will be evaluating the effects of this pattern of work, as well as the condition in the 101 chamber during this season of the year and the condition of the gear left underground. As the team plans for future excavation, those aspects of logistics and conditions underground will be central considerations.

So Becca and Marina and the rest of the team are working this week to help answer those questions. If their work in the 101 chamber goes according to plan, they will move to site 102 before the end of the week.

]]>http://voices.nationalgeographic.com/2014/03/26/a-critical-piece-of-the-hominin-puzzle/feed/2128016Scientists Return to Explore a Second Fossil Chamberhttp://voices.nationalgeographic.com/2014/02/20/scientists-return-to-explore-a-second-fossil-chamber/
http://voices.nationalgeographic.com/2014/02/20/scientists-return-to-explore-a-second-fossil-chamber/#commentsThu, 20 Feb 2014 22:33:55 +0000http://newswatch.nationalgeographic.com/?p=125131Paleoanthropologist and science blogger John Hawks of the University of Wisconsin-Madison has just returned to South Africa with NG Explorer-in-Residence Lee Berger of the University of the Witwatersrand and others to continue work on the hominin discoveries of the Rising Star caves. Follow him on Twitter @JohnHawks.

It has been a long three months since we camped out at the site of the Rising Star caves outside Johannesburg, and the summer growth has erased the signs of our presence. There’s no evidence of the Science Tent, and the paths we wore through the chunks of dolomite are now under grasses and red wildflowers.

Our new goal is to investigate a second hominin locality within the system.

Yesterday we climbed down into the cave once again.

Our small team included Alia Gurtov, Rick Hunter, Pedro Boshoff and team leader Lee Berger. Alia is one of the original six excavators from the fall expedition, and Rick and Pedro helped discover the site. We arrived at the gate in the early morning to do a job — Rick on his motorcycle, Pedro in his car, and the rest of us in Lee’s Jeep. After some hugs and handshakes, we headed up to the cave and geared up.

Most everyone following paleoanthropology by now knows about the chamber that produced more than 1200 numbered specimens. That chamber, inaccessible except through a very narrow 12-meter chute, was the focus of our expedition in November. Since then, a team of scientists from Wits University — including me for the last two weeks — has been working on those bones. Every site represented in the Wits collection has a number; for example, Malapa is site 88. Every specimen plotted by the advance team during our November expedition was tagged in the cave, and given a number beginning with UW-101, for University of the Witwatersrand, site 101.

Every specimen, that is, except for four.

In the final days of the expedition, Rick and Steve Tucker had gone looking through the cave system for more fossils. They found a second area with bones, which we designated site 102. On the last day of our November run, this became the second hominin-bearing locality in the system when Marina Elliott and Becca Peixotto brought out four bone fragments that we could diagnose as hominin.

Return to Site 102

Yesterday we went to investigate this bone assemblage. Our main interest was to get some facts that would help us best plan future excavation. We needed to determine the overall condition of bone in the site, and to see if any of the bones were at risk of disturbance or erosion within the cave.

We headed into the cave, descending by a different route than the one leading to site 101. It may seem strange that after so much time underground in this cave, our team still can be surprised at new passages, but going through the inside of this hillside is a little like playing three-dimensional chess. The cave system is a complex series of multi-layered passages between intersecting fault lines in the dolomite. If you think about the structure of the geology, it begins to makes sense.

That may not help too much when you’re crawling through a narrow tunnel as your friends pass 7 meters overhead.

The five of us clambered down a series of tight drops, then shimmied carefully around a hole ten meters deep. I would soon be on the floor at the bottom of that hole, but happily after a controlled descent.

Self on a shelf in a cave. (Photo credit John Hawks CC-BY-NC-ND)

I do not have what you could call a spelunker’s physique. I did discover that the advantage in caving is not always to the small, as some of the drops benefited from long legs to reach downward. But halfway down our route was a squeeze — a narrow passage between two vertical walls, only around 22 cm wide, the floor sloping downward. For Rick and Alia, that was no problem at all. Either of them could have worn a backpack through it. Lee squeaked it. Pedro and I share the curse of a barrel chest. No chance of getting through.

And so, we headed off toward other parts of the cave to inspect some fossil-bearing breccias (natural concrete-like rock) for signs of australopithecines. Rick, Alia, and Lee went on down, another 20 meters or more vertical distance, to site 102.

Between Rocks and a Hard Place

When they got there, they found the bone assemblage and assessed its condition. They recovered a few additional pieces from the surface of the deposit, recording them and doing field identification of the bone fragments. It was meticulous work, and they took around two hours altogether. Pedro and I found lots of interesting breccia, with carnivores and bovids, but nary a hominin.

I cannot report that the trip was uneventful. As Rick, Alia, and Lee climbed up from site 102, they encountered that squeeze again. Rick and Alia once again breezed through. Not so for Lee — he stuck. I mean really stuck. What had been a relatively straightforward path going down became a very difficult path coming back up, chest wedged between the vertical walls. For forty-five minutes he exerted against the rock.

I propped myself into a vertical shaft, two meters up, and looked down six slices in the dolomite, radiating outward from me like the arms of a snowflake. White sheets of calcite rippled in one of the arms, thin crystals grew in another. Alia sat above me and we waited as Pedro and Rick helped Lee free himself. Ultimately, the breadth of a button made the difference, as he removed his coverall and went through T-shirt only. He emerged tired but exhilarated, having explored where only a handful had ever tread before.

After a rest, we climbed our way back up into the sunlight. The underground world had held us for four hours. It seemed more like one.

Pedro, Lee, a shirtless Rick, and I share a moment of joy after the successful extraction of fossils (and of our fearless leader). (Photo credit John Hawks CC-BY-NC-ND)

More to Come

There are obviously many unanswered questions about site 102. We do not know how it relates to site 101, if at all. They are far apart within the cave system and we do not know any geological reason why the fossils would necessarily represent the same kind of hominin. Until we can examine the specimens more closely, we won’t know what they are.

Still, we learned a lot about site 102, getting a clear idea of the logistics of excavation there in the future. As the expedition ended in November, we left site 101 knowing that there remain thousands of specimens still in the floor of that chamber. Now we know that the system has at least one other excavation area, and the potential for even more.

Meanwhile, we are planning the analysis of fossils from site 101 this May, with the Rising Star Workshop. Read our earlier post to get the basics, but there will be much more on that to come…